The present invention relates to a water cooled panels for burners and/or injectors used in a melting furnace, especially for use in an electric arc furnace (EAF).
In general, an EAF is used to make steel by application of an electric arc to melt one or more of scrap metal and/or other alternative iron bearing feed stocks and alloys that are placed within the furnace. One type of EAF has hemispherical lower bowl made of metal. The bottom and sides of the lower bowl are lined with a refractory material forming the hearth. Extending vertically from the bowl are water-cooled sidewall panels. Extending between the sidewalls over a molten bath of metal (contained by hearth) is a roof. Over the sump area, the balcony ceiling (also called the “banana panel”) may also be provided with water cooled panels. The EAF may also include one or more burners, one or more injectors (such as lances or injectors for injecting particulate solids like carbon), or a combined burner and injector apparatus.
Burners and/or injectors are used in EAFS for the purpose of providing heat and chemical energy to the melt and are typically mounted through holes in water cooled wall panels or sump balcony panels. Burners and/or injectors are subjected to harsh conditions in EAFs, including intense radiative heat from arcing of the electrodes, convective heat transfer from hot furnace gases, slagging caused by splashing slag, and blowback of injected oxygen. In order to prolong the useful life of such burners and/or injectors, they are often mounted in panels, in particular water cooled panels, that at least partially shield them from such harsh conditions. When the burner and/or injector is mounted in the panel, the combined apparatus (the panel and the burner and/or injector) is called a burner and/or injector panel apparatus.
The panel is more or less a protective shield that surrounds the sides of the burner and/or injector but which includes an orifice into which a burner and/or an injector (or injectors) are inserted. The orifice goes through the front face of the panel to allow the fuel and oxidant to be injected (in the case of a burner) or to allow the oxidant and/or solid particles (such as carbon) to be injected (in the case of an injector). The panel may instead have multiple orifices to accommodate both a burner and an injector or a burner and multiple injectors. The panels are typically formed in one or two portions and made of a thermally conductive metal such as cast iron or copper. The water cooling of the burner and/or injector is achieved by a flow of water that follows a circuit (i.e., cooling channel) extending into, through, and out of the metal comprising the panel. Heat absorbed by the metal comprising the panel is transferred to the cooling water so that the panel does not get overheated. This is important because the burner and/or injector contacts the metal comprising the panel at the orifice. If the panel gets overheated, the burner and/or injector will get overheated. The panel can also break causing water leaks posing risk of an explosion.
Currently, there are many different water cooled burner and/or injector panel configurations that are commercially available. These water cooled burner and/or injector panels have a fixed cooling channel length and configuration which results in fixed level of cooling. While water cooled burner and/or injector panels can provide a satisfactory level of cooling for many areas inside an EAF, EAFs also include relatively cooler spots and relatively hotter spots.
Burner and/or injector panels exhibiting a useful lifetime in nominally hot spots often cannot withstand the much hotter conditions in very hot spots without premature failure. Thus, these panels need replacement sooner requiring the EAF to be shut down. Consequently, the long-term steel production rate is decreased. Even if the water cooled burner and/or injector panels that are designed for nominally hot conditions initially provide satisfactory resistance to the above-discussed harsh conditions, a change in the temperature pattern within the EAF can create very hot conditions adjacent that panel. As a result, the panel may still prematurely fail.
Alternatively, the EAF may include only those water cooled burner and/or injector panels that are specifically designed to satisfactorily withstand the harsher conditions of very hot spots. However, since water supplies are often limited at EAFS, the higher requirements for these specially designed panels may exceed the amount of water that is available.
The EAF could be provided with two different types of burner and/or injector panels (one for nominal conditions and one for very hot conditions). This last approach drives up the cost, complexity, and time for manufacturers because two different designs need to be created along with two different types of molds and two different manufacturing processes. It also makes maintenance more difficult.
Various burner panel configurations are disclosed in U.S. Pat. Nos. 4,703,336; 5,444,733; 6,212,218; 6,372,010; 5,166,950; 5,471,495; 6,289,035; 6,614,831; 5,373,530; 5,802,097; 6,999,495; and 6,342,086. Such prior art patents have proven to be beneficial. For example, U.S. Pat. No. 6,999,495 has found wide applicability for increasing spatial energy coverage in a furnace. Likewise, U.S. Pat. No. 6,614,831 has found applicability in extending the reach of various tools, such as a burner or a lance, into the interior of a furnace.
It is an object of the invention to provide a versatile water cooled burner and/or injector panel that overcomes the above deficiencies offered by current practices. More particularly, it is an object of the invention to provide a water cooled burner and/or injector panel that may be simply and economically adapted to nominally hot spots or to very hot spots within an EAF.